Collagen is the most abundant protein in the extracellular matrix of human tissue and plays important roles in providing structural support as well as performing other functions in tissue growth and regeneration. Apart from collagen, other types of extracellular matrix components such as proteoglycans, elastin, etc. also play important roles in maintaining tissue structure and function. Producing scaffolds simulating natural tissue is an essential enabling technology in the tissue engineering industry.
Collagen is an excellent natural biomaterial for tissue engineering because of its close resemblance to nature, low immunogenicity and excellent biocompatibility. However, unprocessed collagen usually has insufficient mechanical properties for it to be useful in engineering tissues in particular the weight-bearing tissues such as tendons, ligaments, intervertebral discs, etc. Unprocessed collagen is also difficult to manipulate and put sutures through during the implantation process. Further, unprocessed collagen is highly water swellable and is vulnerable to enzymatic digestion and thermal denaturation.
Known methods of making collagen membranes often involve extensive extraction procedures and lengthy isolation steps to obtain specific forms of collagen. These procedures often involve coacervation of collagen fibers, de-fatting, multi-cycle vitrification, extensive ultracentrifugation, and electrochemical plating, which are time consuming, difficult to scale up, and expensive. Tanaka, et al., Biomaterials 32:3358-66 (2011) reports on the production of transparent collagen laminates prepared by oriented flow casting, multi-cyclic vitrification, and chemical cross-linking of atelocollagen, which as known in the art is pepsin-solubilized Type I collagen. In addition to the aforementioned disadvantages associated with multi-cyclic vitrification, proteolytic digestion of collagen with enzymes such as pepsin requires strongly acidic conditions. Aside from the insolubility of pepsinized collagen in water, the acidic conditions present difficulties from the standpoint of preparing collagen implants that contain other bioactive materials.
Accordingly, there is a need in the art for methods of preparing collagen implants that do not suffer from one or more of the aforementioned disadvantages.